President Trump on March 27 signed into law the $2 trillion stimulus package designed to save millions of jobs and bail out companies devastated by the coronavirus. But when the dust settled, one hard-hit sector of the travel industry was left on the sidelines: the major cruise lines.

Even politicians who demanded that the industry clean up its environmental record as a condition for receiving taxpayer funds were a little stunned by the news.

“I have to admit I was surprised,” Senator Richard Blumenthal, Democrat of Connecticut, said in an interview, “given the president’s support for the cruise industry.”

So why were the major cruise lines left out? These are the three primary reasons.

“Very emphatically and clearly, the intent of Congress is to exclude the cruise line industry from any assistance with this bill,” Mr. Blumenthal said.

Under the law, companies can only qualify for a loan if they are “created or organized in the United States and under the laws of the United States.”

While the major cruise lines are all headquartered in Miami, they are incorporated in foreign countries: Royal Caribbean is registered in Liberia, Norwegian in Bermuda, and Carnival in Panama.

“If you literally go to the port of Miami and you actually look at the flag on the stern of the ship, you won’t see a U.S. flag flying in the breeze,” said James Walker, a maritime lawyer. “You’ll see the flag of the Bahamas or the flag of Panama.”

The arrangement allows the major cruise lines to operate under the wage and labor laws of the country they’re registered in, paying employees many times less than what they would in the United States. It also grants them access to a century-oldprovision in the tax code that largely exempts them from paying federal income taxes.

In 2019, Carnival paid income tax expenses of $71 million on $20.83 billion in revenue. Royal Caribbean paid $36.2 million in taxes on $10.95 billion in revenue. And Norwegian actually showed a tax benefit, money it is owed, of $18.86 million on $6.46 billion in revenue.

The cruise industry defended its tax and employment policies. Bari Golin-Blaugrund, a spokeswoman for the Cruise Lines International Association, a trade group that represents the industry, said that the cruise industry supports more than 421,000 jobs in the United States and that it follows tax rules for international shipping which have decades-long roots in U.S. tax law.

Questions over environmental record

Earlier in March, a group of eight senators published a letter saying that the cruise industry and airlines should only get a bailout if they took more steps to protect the environment. Days later, a coalition of environmental groups sent a letter to Congress asking lawmakers not to bail out the cruise industry, citing a poor environmental record.

“The cruise sector has a decades-long track record of breaking environmental laws and paying the fines as a matter of doing business,” said Kendra Ulrich of Stand.earth, one of the environmental groups that signed the letter to Congress.

She noted that Princess Cruise Lines, a Carnival Corporation subsidiary, was fined $40 million in 2016 for illegally dumping oil-contaminated waste into the sea, and then covering it up. The company was fined $20 million this year while on probation for discharging plastic into waters around the Bahamas and falsifying records.

In an email, Roger Frizzell, a spokesman for Carnival Corporation, wrote that actions were taken to address the issues that led to the recent fines, including additional oversight, training and equipment to prevent oil spillage, which he said has not happened again on any ship in the fleet. Mr. Frizzell added that the company has undertaken a significant push to “dramatically reduce” and remove single-use plastics on board all of its ships since the 2016 fine.

Ms. Golin-Blaugrund, of the Cruise Line Industry Association, said the cruise industry is committed to responsible tourism, and its environmental policies and practices often exceed those required by law.

Frequently Asked Questions and Advice

Updated June 5, 2020

How many people have lost their jobs due to coronavirus in the U.S.?

The unemployment rate fell to 13.3 percent in May, the Labor Department said on June 5, an unexpected improvement in the nation’s job market as hiring rebounded faster than economists expected. Economists had forecast the unemployment rate to increase to as much as 20 percent, after it hit 14.7 percent in April, which was the highest since the government began keeping official statistics after World War II. But the unemployment rate dipped instead, with employers adding 2.5 million jobs, after more than 20 million jobs were lost in April.

Will protests set off a second viral wave of coronavirus?

Mass protests against police brutality that have brought thousands of people onto the streets in cities across America are raising the specter of new coronavirus outbreaks, prompting political leaders, physicians and public health experts to warn that the crowds could cause a surge in cases. While many political leaders affirmed the right of protesters to express themselves, they urged the demonstrators to wear face masks and maintain social distancing, both to protect themselves and to prevent further community spread of the virus. Some infectious disease experts were reassured by the fact that the protests were held outdoors, saying the open air settings could mitigate the risk of transmission.

How do we start exercising again without hurting ourselves after months of lockdown?

Exercise researchers and physicians have some blunt advice for those of us aiming to return to regular exercise now: Start slowly and then rev up your workouts, also slowly. American adults tended to be about 12 percent less active after the stay-at-home mandates began in March than they were in January. But there are steps you can take to ease your way back into regular exercise safely. First, “start at no more than 50 percent of the exercise you were doing before Covid,” says Dr. Monica Rho, the chief of musculoskeletal medicine at the Shirley Ryan AbilityLab in Chicago. Thread in some preparatory squats, too, she advises. “When you haven’t been exercising, you lose muscle mass.” Expect some muscle twinges after these preliminary, post-lockdown sessions, especially a day or two later. But sudden or increasing pain during exercise is a clarion call to stop and return home.

My state is reopening. Is it safe to go out?

States are reopening bit by bit. This means that more public spaces are available for use and more and more businesses are being allowed to open again. The federal government is largely leaving the decision up to states, and some state leaders are leaving the decision up to local authorities. Even if you aren’t being told to stay at home, it’s still a good idea to limit trips outside and your interaction with other people.

What’s the risk of catching coronavirus from a surface?

Touching contaminated objects and then infecting ourselves with the germs is not typically how the virus spreads. But it can happen. A number of studies of flu, rhinovirus, coronavirus and other microbes have shown that respiratory illnesses, including the new coronavirus, can spread by touching contaminated surfaces, particularly in places like day care centers, offices and hospitals. But a long chain of events has to happen for the disease to spread that way. The best way to protect yourself from coronavirus — whether it’s surface transmission or close human contact — is still social distancing, washing your hands, not touching your face and wearing masks.

How can I protect myself while flying?

If air travel is unavoidable, there are some steps you can take to protect yourself. Most important: Wash your hands often, and stop touching your face. If possible, choose a window seat. A study from Emory University found that during flu season, the safest place to sit on a plane is by a window, as people sitting in window seats had less contact with potentially sick people. Disinfect hard surfaces. When you get to your seat and your hands are clean, use disinfecting wipes to clean the hard surfaces at your seat like the head and arm rest, the seatbelt buckle, the remote, screen, seat back pocket and the tray table. If the seat is hard and nonporous or leather or pleather, you can wipe that down, too. (Using wipes on upholstered seats could lead to a wet seat and spreading of germs rather than killing them.)

Should I wear a mask?

The C.D.C. has recommended that all Americans wear cloth masks if they go out in public. This is a shift in federal guidance reflecting new concerns that the coronavirus is being spread by infected people who have no symptoms. Until now, the C.D.C., like the W.H.O., has advised that ordinary people don’t need to wear masks unless they are sick and coughing. Part of the reason was to preserve medical-grade masks for health care workers who desperately need them at a time when they are in continuously short supply. Masks don’t replace hand washing and social distancing.

What should I do if I feel sick?

If you’ve been exposed to the coronavirus or think you have, and have a fever or symptoms like a cough or difficulty breathing, call a doctor. They should give you advice on whether you should be tested, how to get tested, and how to seek medical treatment without potentially infecting or exposing others.

It was a public-relations nightmare, and eventually the State Department stepped in and warned Americans, especially those with underlying health issues, not to board cruise ships. After the warning, the major cruise lines suspended U.S. operations for 30 days.

The optics for the industry are not great at the moment, said James Hardiman, the managing director of leisure equity research for Wedbush Securities, who follows the industry.

“I think if the U.S. public turns on the television and they see a bunch of people getting back on a cruise ship anytime soon, I think the public reaction to that is going to be very much akin to the public reaction when you saw a bunch of spring breakers getting drunk and ignoring the new reality,” he said.

The perception that going on a cruise is synonymous with bad or irresponsible behavior, he said, “is going to be a real problem for the industry.”

But cruise industry officials defended their actions. Mr. Frizzell wrote in an email that Carnival Corporation responded quickly to news of the outbreak in Asia — well before other industries. He added that Carnival enacted a raft of changes in response to the virus including restricting passengers who had traveled to China, instituting temperature checks and health screenings, and canceling cruises to infected areas.